In many instances it is desirable or necessary to provide limited and restricted access to certain components of a vehicle such as a motor vehicle. For example, when parking a car in a parking lot, it is often necessary to give the car's ignition key to an attendant so that the car can be conveniently moved if necessary. Similarly, when making use of a valet parking service, it is necessary to give a car's ignition key to a valet. At the same time, however, it is clearly generally desirable to limit the attendant or valet's access to certan components or parts of the car such as the trunk, the glove compartment, etc.
Accordingly, many cars have two different keys, one of which (the master key) operates the car's ignition system as well as all other locks (for example, the doors, the trunk, the glove compartment, the fuel door, etc.) and the other of which (the valet key) is limited to the ignition system and the doors. Some cars allow the trunk and fuel door to be opened from within the car, for example, by pulling a lever or pressing a button. It should be noted that in some cases cars are provided only with a single key and therefore no means at all to deny access by a valet to the trunk, glove compartment, etc.
Using the two-key system, various parts of a car can be made inaccessible to a valet, lot attendant and the like.
In some of the more expensive motor vehicles, all externally operable locks (except the door locks) have been eliminated. This helps prevent unauthorized access by those who would pick the locks or remove them to gain access. The trunk and fuel door have electric locks which can be operated using buttons on the dashboard and buttons on a remote control.
There are other approaches to limiting and/or controlling vehicle access. For example, some cars have a button or switch which must be pressed in order to switch to valet mode. One example of this is found in the 1998Cadillac Eldorado which has a valet mode which is activated by a valet button in the car's glove compartment. Once the button is pressed, the glove compartment must be locked with a special glove compartment key. In this car the ignition or master key does not open the glove compartment.
These two-key systems of access control have a number of problems, including, at a minimum, that they require that two keys be carried and separated whenever a valet or like service is used. If the wrong key is mistakenly given to a valet or lot attendant then security is lost. Second, the two-key systems effectively require a car to be divided into two distinct and fixed zones, one of which is accessible only with the master key.